Unconscious mind activates central cardiovascular network and promotes adaptation to microgravity possibly anti-aging during 1-year-long spaceflight

Abstract

The intrinsic cardiovascular regulatory system (β, 0.00013–0.02 Hz) did not adapt to microgravity after a 6-month spaceflight. The infraslow oscillation (ISO, 0.01–0.10 Hz) coordinating brain dynamics via thalamic astrocytes plays a key role in the adaptation to novel environments. We investigate the adaptive process of a healthy astronaut during a 12-month-long spaceflight by analyzing heart rate variability (HRV) in the LF (0.01–0.05 Hz) and MF1 (0.05–0.10 Hz) bands for two consecutive days on four occasions: before launch, at 1-month (ISS01) and 11-month (ISS02) in space, and after return to Earth. Alteration of β during ISS01 improved during ISS02 (P = 0.0167). During ISS01, LF and MF1 bands, reflecting default mode network (DMN) activity, started to increase at night (by 43.1% and 32.0%, respectively), when suprachiasmatic astrocytes are most active, followed by a 25.9% increase in MF1-band throughout the entire day during ISS02, larger at night (47.4%) than during daytime. Magnetic declination correlated positively with β during ISS01 (r = 0.6706, P < 0.0001) and ISS02 (r = 0.3958, P = 0.0095). Magnetic fluctuations may affect suprachiasmatic astrocytes, and the DMN involving ISOs and thalamic astrocytes may then be activated, first at night, then during the entire day, a mechanism that could perhaps promote an anti-aging effect noted in other investigations.

Biological 12-hour rhythm facilitates re-entrainment from circadian desynchrony and promotes psychological resilience during long-duration spaceflight

“…Twenty healthy astronauts who spent about 6 months in space gave us a unique opportunity to examine the adaptive process of neuro-cardiovascular coordination. We obtained new evidence that the 12-h biological rhythm facilitated the rapid adaptation to microgravity in space (Table 1), supporting results from our previous case report [19], while the circadian system plays a key role in the adaptation to the novel space environment [14,15,17,18]. The response of the 12-h rhythm appeared early, after about 21 days in space (ISS01), and it was larger than the circadian response (Table 2).…”

“…Astronauts follow a strict 24-h routine, waking up at 06:00 and retiring for sleep at 21:30. At the time of data collection, arti cial lighting from both incandescent and uorescent light sources was used on the ISS; maximal light intensity was 700 lx [15,16,17,18,19].…”

“…Sleep duration at night was estimated by using circadian pro les of RR-intervals and 5-min HF endpoints of HRV [14,18,53]. Sleep quality was assessed based on whether a sleep-related increase in RR-intervals and in HRV-HF could be observed [18,19]. When 48-h ECG were recorded, HRV endpoints and sleep duration were averaged over the two consecutive sleep spans.…”

“…The 12-h rhythm provides an evolutionary advantage in mammals, including humans [25,28,30,33,63,64]. Previously, we reported that the 12-h component can be important for the rapid adaptation to microgravity in space [19]. Herein, we observed how the 12-h rhythm participated in antiaging effects, contributing to an ampli ed circadian rhythm of HR (Table 1), increases in SDNN, SDANN5 and SDANN30 (Table 3), counteracting internal desynchrony (Table 4, Fig.…”

“…Several lessons were learned from our previous investigations [13,14,15,16,17,18,19]. (1) We observed that adaptive processes in space are circadian stage-dependent, starting at night and later spreading to the entire day.…”